Cubic-phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte, electrolyte membrane, preparation method of electrolyte membrane and solid-state battery

Abstract

The invention discloses a cubic-phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte, an electrolyte membrane, a preparation method of the electrolyte membrane and a solid-state battery, and relates to the technical field of batteries. The preparation method of the cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte comprises the following steps: mixing a lithium source, a lanthanum source, a zirconium source and a doping source, calcining at 800-1100 DEG C for 3-12 hours, and cooling to obtain the cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte, the doping source comprises at least three of the following elements: Cs, Rb, Ga, Al, Fe, Ge, Ta, Nb, Si, Sb, Te, W, Mo, Cr, Gd, Y, Mg, Sc, B, Ce, Sr, Ca and Nd. The multi-element doped lithium lanthanum zirconium oxide solid electrolyte is prepared by utilizing a high-entropy effect and a slow diffusion effect, so that the multi-element doped lithium lanthanum zirconium oxide solid electrolyte is stabilized in a cubic phase, and the ionic conductivity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a cubic phase multi-element doped lithium lanthanum zirconium oxygen solid electrolyte, an electrolyte film and a preparation method thereof and a solid-state battery. BACKGROUND

[0002] Lithium ion batteries have long cycle life, high energy density, wide operating temperature window, green environmental protection and relatively simple production process, and have broad application prospects in the fields of new energy vehicles, mobile electronic products and power grid energy storage. However, the traditional lithium ion battery using organic electrolyte has safety hazards such as leakage, combustion and explosion of electrolyte. The all-solid-state and semi-solid-state lithium ion battery replaces the flammable organic electrolyte in the traditional lithium ion battery with non-flammable, high-melting-point ceramic electrolyte or organic solid-state and semi-solid-state electrolyte, which fundamentally reduces or even removes the flammable material; at the same time, the all-solid-state and semi-solid-state electrolyte has much better mechanical properties than the liquid electrolyte, which can prevent the short circuit of the battery caused by the penetration of lithium dendrites through the positive and negative electrode separators, and avoid the occurrence of thermal runaway. Therefore, the all-solid-state and semi-solid-state lithium ion battery has become one of the main development directions to improve the safety of lithium ion batteries, and the all-solid-state and semi-solid-state electrolyte has attracted widespread attention in the industrial and academic research fields.

[0003] Common oxide-based inorganic solid-state electrolytes can be divided into garnet-type, perovskite-type, sodium fast ion conductor-type, etc. Among them, the garnet-type solid-state electrolyte represented by lithium lanthanum niobium oxide / lithium lanthanum tantalum oxide (Li5La3(Ni / Ta)2O 12 , LLNO / LLTO) reported in 2003 and lithium lanthanum zirconium oxide (LLZO, such as Li7La3Zr2O 12 ) reported in 2007 has the advantage of good chemical stability and will not react with the positive and negative electrodes. In addition, the garnet-type solid-state electrolyte has good electrochemical stability, and the electrochemical stability window is as high as 6V. Compared with LLNO / LLTO, LLZO has higher room temperature ionic conductivity. LLZO has two different crystal structures, low-temperature / room-temperature stable tetragonal phase (t-LLZO) and high-temperature metastable cubic phase (c-LLZO). The decrease of site density and the increase of crystal phase filling rate result in that the ionic conductivity of t-LLZO at room temperature is much lower than that of c-LLZO, with a difference of two orders of magnitude. In summary, stabilizing the cubic phase of LLZO and improving the room temperature ionic conductivity are challenges that the development of garnet-type solid-state electrolyte needs to face.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] Based on the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a cubic-phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte, an electrolyte membrane, a preparation method thereof, and a solid-state battery, aiming to provide a method for stabilizing the LLZO solid electrolyte in the cubic phase to improve the room-temperature ionic conductivity.

[0006] The technical solution of the present invention is as follows: In the first aspect of the present invention, a preparation method of a cubic-phase multi-element doped LLZO solid electrolyte is provided, which includes the following steps: Providing a mixed powder, wherein the mixed powder includes a lithium source, a lanthanum source, a zirconium source, and a doping source; Calcining the mixed powder at a temperature of 800-1100°C for 3-12 hours, and after cooling, obtaining the cubic-phase multi-element doped LLZO solid electrolyte; The elements contained in the doping source include at least three of the following elements: Cs, Rb, Ga, Al, Fe, Ge, Ta, Nb, Si, Sb, Te, W, Mo, Cr, Gd, Y, Mg, Sc, B, Ce, Sr, Ca, and Nd.

[0007] Optionally, the preparation method of the mixed powder includes the following steps: Weighing the lithium source, the lanthanum source, the zirconium source, and the doping source according to the stoichiometric ratio of each element in the cubic-phase multi-element LLZO solid electrolyte, and ball-milling the lithium source, the lanthanum source, the zirconium source, and the doping source, and the lithium in the lithium source is in excess of 10%-60%, obtaining the mixed powder; Among them, the elements and the stoichiometric ratio of the elements contained in the cubic-phase multi-element doped LLZO solid electrolyte are calculated based on Li a M b La c N d Zr e Q f O 12 Calculating, 0 < a ≤ 7, 0 < b ≤ 7, 0 < c ≤ 3, 0 < d ≤ 9, 0 < e ≤ 2, 0 ≤ f ≤ 8; the doping source includes a first doping source, a second doping source, and a third doping source, M is the element contained in the first doping source, N is the element contained in the second doping source, and Q is the element contained in the third doping source.

[0008] Optionally, the lithium source includes at least one of lithium carbonate and lithium oxide; and / or, The lanthanum source includes at least one of lanthanum oxide and lanthanum carbonate; and / or, The zirconium source includes at least one of zirconium dioxide and zirconium carbonate.

[0009] Optionally, the doping source includes cesium carbonate, rubidium carbonate, and gallium oxide.

[0010] Optionally, the ball milling method is dry ball milling or wet ball milling. The dispersion liquid of the wet ball milling includes at least one of ethanol, isopropyl alcohol and n-butanol. The rotation speed of the wet ball milling is 400-800 rpm, and the time of the wet ball milling is 8-15 h.

[0011] In a second aspect of the present application, a cubic phase multi-element doped LLZO solid-state electrolyte is provided, wherein the cubic phase multi-element doped LLZO solid-state electrolyte is prepared by the preparation method of the present application.

[0012] In a third aspect of the present application, an electrolyte film is provided, wherein the electrolyte film includes an electrolyte, and the solid-state electrolyte film includes the cubic phase multi-element doped LLZO solid-state electrolyte of the present application.

[0013] Optionally, the electrolyte film includes a polymer-based film, and lithium salt and the cubic phase multi-element doped LLZO solid-state electrolyte dispersed in the polymer-based film.

[0014] In a fourth aspect of the present application, a preparation method of an electrolyte film is provided, wherein the method includes the following steps: dispersing lithium salt, a solid-state electrolyte and a polymer material in an organic solvent to obtain a mixed liquid; after casting or electrospinning the mixed liquid, drying to obtain the electrolyte film; The solid-state electrolyte includes the cubic phase multi-element doped LLZO solid-state electrolyte of the present application.

[0015] In a fifth aspect of the present application, a solid-state battery is provided, wherein the solid-state battery includes a positive electrode, a negative electrode and an electrolyte film between the positive electrode and the negative electrode, and the electrolyte film is the electrolyte film of the present application or is prepared by the preparation method of the present application. Beneficial effects: The cubic phase multi-element doped LLZO solid-state electrolyte material is prepared by using the high-entropy effect and slow diffusion effect of high-entropy doping. The high-entropy effect increases the compatibility between the main elements, so that the material tends to generate a simple solid solution (cubic phase is simpler than tetragonal phase). The slow diffusion effect slows down the diffusion speed of elements other than lithium, which is beneficial to the formation of cubic phase at high temperature and the stabilization of cubic phase (instead of tetragonal phase) during the cooling process. Therefore, the method of high-entropy doping provided by the present application can stabilize the multi-element doped LLZO solid-state electrolyte in the cubic phase and improve the ionic conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A schematic diagram of a preparation process of the cubic phase multi-element doped LLZO solid electrolyte.

[0017] Figure 2 A schematic diagram of a preparation process of the electrolyte film.

[0018] Figure 3 XRD patterns of the cubic phase multi-element doped LLZO solid electrolyte in Example 1 and Example 2.

[0019] Figure 4 SEM and EDS patterns of the cubic phase multi-element doped LLZO solid electrolyte prepared in Example 1, wherein (a) is the SEM pattern, and (b) is the EDS pattern of the corresponding area of (a).

[0020] Figure 5 Schematic diagrams of different battery structures, wherein (a) is a symmetric battery, and (b) is a half battery.

[0021] Figure 6 EIS patterns of the symmetric battery based on the electrolyte film in Example 4, Example 5, Comparative Example 1 and Comparative Example 2.

[0022] Figure 7 Cycle performance diagrams of the half battery based on the electrolyte film in Example 4, Example 5, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0023] The present application provides a cubic phase multi-element doped LLZO solid electrolyte, an electrolyte film, a preparation method thereof and a solid-state battery. In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application is only for the purpose of describing the specific embodiments and is not intended to limit the present application.

[0025] If the present application involves the description of "first", "second", etc. in the embodiments, the description of "first", "second", etc. is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features.

[0026] The inventor has found that the entropy stabilization effect of high-entropy alloy (referring to a single-phase solid solution alloy with more than four components) helps to improve the crystal phase stability. Therefore, the present application combines the entropy stabilization theory of high-entropy alloy with the doping of LLZO to synthesize a multi-element doped LLZO solid electrolyte material, and the high-entropy doping stabilizes the crystal phase of LLZO and improves the ionic conductivity. Specifically, the present application provides a preparation method of cubic phase multi-element doped LLZO solid electrolyte, which comprises the following steps as shown in the following formula: Figure 1 S11, providing a mixed powder, wherein the mixed powder comprises a lithium source, a lanthanum source, a zirconium source and a doping source; the doping source contains at least three of the following elements: Cs, Rb, Ga, Al, Fe, Ge, Ta, Nb, Si, Sb, Te, W, Mo, Cr, Gd, Y, Mg, Sc, B, Ce, Sr, Ca and Nd; S12, calcining the mixed powder at a temperature of 800-1100℃ for 3-12h, and obtaining the cubic phase multi-element doped LLZO solid electrolyte after cooling (such as natural cooling).

[0027] The present application utilizes the high-entropy effect and slow diffusion effect of high-entropy doping to prepare the cubic phase multi-element doped LLZO solid electrolyte material. The high-entropy effect increases the compatibility between the main elements, so that the material tends to form a simple solid solution (cubic phase is simpler than tetragonal phase). The slow diffusion effect slows down the diffusion speed of elements other than lithium, which is beneficial to the formation of cubic phase at high temperature and the stabilization of cubic phase during the cooling process (instead of forming tetragonal phase due to diffusion). Therefore, the method of high-entropy doping provided by the present application can stabilize the multi-element doped LLZO solid electrolyte in the cubic phase and improve the ionic conductivity.

[0028] In addition, with the increase of the number of doping elements, the system mixing entropy increases, and the entropy stabilization effect is more significant, so that the multi-element doped LLZO solid electrolyte with more stable cubic phase crystal phase can be obtained.

[0029] In step S1, in some embodiments, at least one of the lithium source, the lanthanum source, the zirconium source and the doping source is an oxide or a carbonate.

[0030] In some embodiments, the preparation method of the mixed powder comprises the following steps: According to the stoichiometric ratio of each element in the cubic phase multi-element LLZO solid electrolyte, the lithium source, the lanthanum source, the zirconium source and the doping source are weighed, and the lithium source, the lanthanum source, the zirconium source and the doping source are ball milled, and the lithium in the lithium source is excessive by 10%-60%; ​wherein the elements contained in the cubic phase multi-element doped LLZO solid-state electrolyte and the stoichiometric ratio of the elements are Li a M b La c N d Zr e Q f O 12 , 0 < b ≤ 7, 0 < c ≤ 3, 0 < d ≤ 9, 0 < e ≤ 2, 0 ≤ f ≤ 8; the doping source includes a first doping source (including one or more compounds), a second doping source (including one or more compounds), and a third doping source (including one or more compounds), M is an element (including one or more elements) contained in the first doping source, N is an element (including one or more elements) contained in the second doping source, and Q is an element (including one or more elements) contained in the third doping source. For example, when the second doping source contains two compounds, N includes two elements.

[0031] In some embodiments, the lithium in the lithium source is in excess by 10-40%.

[0032] In some embodiments, the lithium in the lithium source is in excess by 10-15%. For example, when the cubic phase multi-element doped LLZO solid-state electrolyte contains Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 , the doping source includes a gallium source, a rubidium source, and a cesium source, the lithium source, the gallium source, the lanthanum source, the rubidium source, the cesium source, and the zirconium source are weighed according to the molar ratio of lithium (Li) in the lithium source, gallium (Ga) in the gallium source, lanthanum (La) in the lanthanum source, rubidium (Rb) in the rubidium source, cesium (Cs) in the cesium source, and zirconium (Zr) in the zirconium source as 6.5x (110%-115%):0.3:2.8:0.1:0.1:2, i.e., the lithium source, the gallium source, the lanthanum source, the rubidium source, the cesium source, and the zirconium source are weighed according to the molar ratio of Li, Ga, La, Rb, Cs, and Zr as (7.15-7.475):0.3:2.8:0.1:0.1:2.

[0033] In some embodiments, the lithium in the lithium source is in excess by 10-40%. In some embodiments, the lithium in the lithium source is in excess by 10-15%.

[0034] In some embodiments, the lithium source includes at least one of lithium carbonate and lithium oxide, but is not limited thereto.

[0035] In some embodiments, the lanthanum source includes at least one of lanthanum oxide and lanthanum carbonate, but is not limited thereto.

[0036] In some embodiments, the zirconium source includes at least one of zirconium dioxide and zirconium carbonate, but is not limited thereto.

[0037] In some embodiments, the doping source includes cesium carbonate, rubidium carbonate and gallium oxide.

[0038] In some embodiments, the ball milling method is a dry ball milling method or a wet ball milling method.

[0039] In some embodiments, the dispersion liquid of the wet ball milling method includes at least one of ethanol, isopropyl alcohol and n-butyl alcohol.

[0040] In some embodiments, the rotation speed of the wet ball milling method is 400-800 rpm (for example, can be 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, etc.), and the time of the wet ball milling method is 8-15 h (for example, can be 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h or 15 h, etc.).

[0041] The embodiment of the present application further provides a cubic phase multi-element doped LLZO solid-state electrolyte, wherein the cubic phase multi-element doped LLZO solid-state electrolyte is prepared by the preparation method of the present application.

[0042] The embodiment of the present application further provides an electrolyte film, wherein the electrolyte film includes a solid-state electrolyte, and the electrolyte film includes the cubic phase multi-element doped LLZO solid-state electrolyte of the present application.

[0043] In the embodiment of the present application, the electrolyte film has high ionic conductivity and cycle stability.

[0044] In some embodiments, the electrolyte film includes a polymer-based film and lithium salt and cubic phase multi-element doped LLZO solid-state electrolyte dispersed in the polymer-based film.

[0045] In some embodiments, the lithium salt includes at least one of lithium bis-trifluoromethanesulfonimide (LiTFSI), lithium bis-fluorosulfonimide (LiFSI), lithium bis-oxalato-borate (LiBOB), lithium thiophosphate (Li3PS4), lithium hexafluorophosphate (LiPF6) and lithium perchlorate (LiClO4), but is not limited thereto.

[0046] In some embodiments, the polymer-based film includes one of a polyethylene oxide (PEO)-based film, a polyacrylonitrile-based film, a polyvinylidene fluoride-based film and a polycarbonate-based film, but is not limited thereto.

[0047] The application takes the prepared cubic phase multi-element doped LLZO solid-state electrolyte as a filler, disperses it in a PEO-based film, thereby improving the performance of the PEO-based high molecular polymer electrolyte. PEO has low cost, can dissolve various lithium salts, and has good chemical and electrochemical stability. However, the lithium ion conductivity of the conventional PEO-lithium salt semi-solid electrolyte system is low, which cannot meet the commercial needs. The electrolyte film provided by the application has high ion conductivity and cycle stability.

[0048] The application also provides a preparation method of the electrolyte film, which comprises the following steps as shown in the figure: Figure 2 S21, dispersing lithium salt, cubic phase multi-element doped LLZO solid-state electrolyte and polymer material in an organic solvent to obtain a mixed solution; S22, pouring or electrospinning the mixed solution, and then drying to obtain the electrolyte film.

[0049] The preparation method provided by the application is simple, and the prepared electrolyte film has high ion conductivity and cycle stability.

[0050] In step S21, the lithium salt and the polymer material are selected as described above, and will not be described here.

[0051] In some embodiments, the organic solvent includes but is not limited to acetonitrile.

[0052] The application also provides a solid-state battery, which comprises a positive electrode, a negative electrode and an electrolyte film between the positive electrode and the negative electrode, wherein the electrolyte film is the electrolyte film described above or prepared by the preparation method described above. The positive electrode comprises a positive electrode material, which includes one of lithium cobaltate, high-nickel ternary oxide (lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide) and lithium-rich manganese-based oxide, but is not limited thereto.

[0053] The negative electrode includes one of a lithium metal negative electrode, a graphite negative electrode and a silicon-carbon negative electrode, but is not limited thereto.

[0054] The application will be further described below through specific embodiments.

[0055] Embodiment 1 The embodiment provides a preparation method of cubic phase multi-element doped LLZO solid-state electrolyte (i.e. cubic phase Cs, Rb and Ga co-doped LLZO solid-state electrolyte), which comprises the following steps: According to Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs​0.1 Zr2O 12 The stoichiometric ratio of each element was determined by weighing lithium carbonate (with lithium in excess by 10%), lanthanum oxide, zirconium dioxide, cesium carbonate, rubidium carbonate, and gallium oxide, and adding them to ethanol (the ratio of zirconium dioxide to ethanol is 0.47 mol : 1 L). The mixture was then ball-milled at 600 rpm for 10 hours to obtain a mixed powder (white powder). The mixed powder was calcined at 900℃ for 6 hours and then naturally cooled to obtain a cubic Cs, Rb, and Ga co-doped LLZO solid electrolyte, denoted as Li. 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 .

[0056] Its XRD pattern is as follows Figure 3 As shown, Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 It has a cubic phase structure, meaning that the preparation method provided by this invention can make Li... 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 It is stabilized in the cubic phase, with La2Zr2O7 as a byproduct.

[0057] Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 Scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) images are as follows: Figure 4 As shown, Cs, Rb, and Ga elements were detected, indicating that the preparation method provided in this embodiment achieves co-doping of Cs, Rb, and Ga.

[0058] Example 2 This embodiment provides a method for preparing a cubic phase multi-element doped LLZO solid electrolyte (i.e., cubic phase Cs, Rb and Ga co-doped LLZO solid electrolyte), which differs from Example 1 only in that the lithium in the lithium carbonate is in 15% excess.

[0059] Its XRD pattern is as follows Figure 3 As shown, Li 6.5 Ga 0.3 La 2.8 Rb0.1 Cs 0.1 Zr2O 12 is cubic phase structure, i.e. the preparation method provided by the present application can make Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 is stabilized in cubic phase, and Li2ZrO3 is by-product.

[0060] When lithium in lithium carbonate (Li2CO3) is 10% excess, Li overflow produces La2Zr2O7 by-product. When lithium in lithium carbonate is 15% excess, Li is excess and La is insufficient, producing Li2ZrO3 by-product. This shows that the optimal amount of lithium carbonate is between 10% and 15% excess of lithium. The excess addition of Li2CO3 between the two ratios can minimize the by-products produced due to excess or insufficient Li.

[0061] Example 3 The present embodiment provides a preparation method of cubic phase multi-element doped LLZO solid electrolyte (i.e. cubic phase Cs, Rb and Ga co-doped LLZO solid electrolyte), comprising the following steps: According to the stoichiometric ratio of each element in Li 6.3 Ga 0.3 La 2.9 Rb 0.05 Cs 0.05 Zr2O 12 , take lithium carbonate (15% excess of lithium), lanthanum oxide, zirconium dioxide, cesium carbonate, rubidium carbonate and gallium oxide and add them to ethanol (the ratio of zirconium dioxide to ethanol is 0.47 mol: 1L), and ball mill at a speed of 600 rpm for 10 hours to obtain a mixed powder (white powder); The mixed powder is calcined at 900°C for 6h and naturally cooled to obtain a Cs, Rb and Ga co-doped LLZO solid electrolyte, denoted as Li 6.3 Ga 0.3 La 2.9 Rb 0.05 Cs 0.05 Zr2O 12 .

[0062] Example 4 The present embodiment provides a preparation method of electrolyte film, which is prepared by one-step solution casting method, comprising the following steps: 0.24g of LiTFSI, 0.063g of Li 6.5 Ga 0.3 La 2.8 Rb0.1 Cs 0.1 Zr2O 12 Add to 20 mL of acetonitrile solvent and sonicate for 6 h to ensure the aggregation of Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 Complete dispersion. Add 0.6 g PEO (Rhohn's reagent, molecular weight MW = 600,000) to the dispersed system and stir at 60 °C for 12 h until PEO is completely dissolved in acetonitrile solution to obtain a mixture; The mixture was poured into a PTFE culture dish with a diameter of 90 mm and dried naturally in an argon atmosphere for 96 h, followed by drying under vacuum at 60 °C for 12 h to obtain an electrolyte membrane.

[0063] Example 5 This embodiment provides a method for preparing an electrolyte membrane using a one-step solution casting method, comprising the following steps: 0.24g of LiTFSI and 0.063g of Li from Example 3 were added. 6.3 Ga 0.3 La 2.9 Rb 0.05 Cs 0.05 Zr2O 12 Add to 20 mL of acetonitrile solvent and sonicate for 6 h to ensure the aggregation of Li 6.3 Ga 0.3 La 2.9 Rb 0.05 Cs 0.05 Zr2O 12 Complete dispersion. Add 0.6 g PEO (Rhohn's reagent, molecular weight MW = 600,000) to the dispersed system and stir at 60 °C for 12 h until PEO is completely dissolved in acetonitrile solution to obtain a mixture; The mixture was poured into a PTFE culture dish with a diameter of 90 mm and dried naturally in an argon atmosphere for 96 h, followed by drying under vacuum at 60 °C for 12 h to obtain an electrolyte membrane.

[0064] Comparative Example 1 This comparative example provides a method for preparing an electrolyte membrane, which differs from Example 4 only in that Li is not added. 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 .

[0065] Comparative Example 2 The comparative example provides a preparation method of an electrolyte film, which is only different from that of Example 4 in that Li 6.5 Ga 0.3 La 2.8 Rb 0.1 Cs 0.1 Zr2O 12 is replaced by commercial LLZO (i.e. Li7La3Zr2O 12 ).

[0066] In order to facilitate performance comparison with the commercial LLZO (the median particle size is 400 nm), the sand milling method is used to further reduce the particle size of the solid electrolyte prepared in the examples. The zirconium bead with a particle size of 0.6-0.8 mm and 0.1 mm is used for sand milling for 8 h, so that the median particle size of the solid electrolyte prepared in the examples is reduced to about 400 nm, and then the following tests are performed: According to (a) shown in Figure 5 , the electrolyte films in Example 4, Example 5, Comparative Example 1 and Comparative Example 2 are assembled into symmetric batteries in the order of positive shell, stainless steel gasket, electrolyte film, stainless steel gasket, stainless steel spring and negative shell, and the symmetric batteries are subjected to electrochemical impedance spectroscopy (EIS) test, and the results are shown in Figure 6 . It can be seen that the ionic conductivity of the electrolyte film prepared in the present application is better than that of the electrolyte film based on the commercial LLZO.

[0067] According to (b) shown in Figure 5 , the electrolyte films in Example 4, Example 5, Comparative Example 1 and Comparative Example 2 are assembled into half batteries in the order of positive shell, stainless steel gasket, lithium cobalt oxide positive electrode, electrolyte film, lithium metal negative electrode, stainless steel gasket, stainless steel spring and negative shell, and the half batteries are subjected to cycle stability test (0.2C charging and 0.2C discharging), and the results are shown in Figure 7 . It can be seen that the cycle stability of the electrolyte film provided in the present application is better than that of the electrolyte film based on the commercial LLZO, and has the effect of improving the specific capacity of the lithium cobalt oxide half battery.

[0068] In summary, the application provides cubic phase multi-element doped LLZO solid electrolyte, electrolyte film and preparation method thereof and solid-state battery. The application utilizes high-entropy effect and slow diffusion effect of high-entropy doping to prepare cubic phase multi-element doped LLZO solid electrolyte material. The high-entropy effect increases the compatibility between main elements, so that the material is more inclined to generate a simple solid solution (cubic phase is simpler than tetragonal phase). The slow diffusion effect slows down the diffusion speed of elements other than lithium, which is conducive to the formation of cubic phase at high temperature and the stabilization of cubic phase (rather than tetragonal phase) during the cooling process. Since lithium has a small ionic radius, it is basically not affected by the slow diffusion effect. Therefore, the method of high-entropy doping provided by the application can stabilize the multi-element doped LLZO solid electrolyte in the cubic phase and improve the ionic conductivity.

[0069] It should be understood that the application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the application.

Claims

1. A method of making a cubic phase multi-element doped lithium lanthanum zirconium oxide solid state electrolyte, characterized by, The method comprises the following steps: Providing a mixed powder comprising a lithium source, a lanthanum source, a zirconium source and a doping source; Firing the mixed powder at a temperature of 800-1100℃ for 3-12h, and obtaining the cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte after cooling; The doping source contains at least three of the following elements: Cs, Rb, Ga, Al, Fe, Ge, Ta, Nb, Si, Sb, Te, W, Mo, Cr, Gd, Y, Mg, Sc, B, Ce, Sr, Ca and Nd.

2. The production method according to claim 1, characterized by, The preparation method of the mixed powder comprises the following steps: According to the stoichiometric ratio of each element in the cubic phase multi-element lithium lanthanum zirconium oxide solid electrolyte, the lithium source, the lanthanum source, the zirconium source and the doping source are weighed, and the lithium source, the lanthanum source, the zirconium source and the doping source are ball milled, and the lithium in the lithium source is excessive by 10%-60%, to obtain the mixed powder; The stoichiometric ratio of the elements contained in the cubic phase multi-element doped lithium lanthanum zirconium oxygen solid electrolyte is Li a M b La c N d Zr e Q f O 12 The calculation is 0 The doping source includes a first doping source, a second doping source and a third doping source, M is an element contained in the first doping source, N is an element contained in the second doping source, and Q is an element contained in the third doping source.

3. The preparation method according to claim 1, characterized in that, The lithium source comprises at least one of lithium carbonate and lithium oxide; and / or, The lanthanum source comprises at least one of lanthanum oxide and lanthanum carbonate; and / or, The zirconium source comprises at least one of zirconium dioxide and zirconium carbonate.

4. The preparation method according to claim 1, characterized in that, The doping source comprises cesium carbonate, rubidium carbonate and gallium oxide.

5. The preparation method according to claim 2, characterized in that, The ball milling method is dry ball milling or wet ball milling; The dispersion liquid of the wet ball milling comprises at least one of ethanol, isopropyl alcohol and n-butanol; The rotation speed of the wet ball milling is 400-800rpm, and the time of the wet ball milling is 8-15h.

6. A cubic phase multi-element doped lithium lanthanum zirconium oxide solid state electrolyte, characterized in that, The cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte is prepared by the preparation method of any one of claims 1-5.

7. An electrolyte membrane, characterized by, The electrolyte film comprises a solid electrolyte, and the electrolyte film comprises the cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte of claim 6.

8. The electrolyte film according to claim 7, characterized by The electrolyte film comprises a polymer-based film and lithium salt and cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte dispersed in the polymer-based film.

9. A method for producing an electrolyte membrane, characterized by, The method comprises the following steps: Dispersing the lithium salt, the solid electrolyte and the polymer material in an organic solvent to obtain a mixed liquid; After pouring or electrospinning the mixed liquid, drying is performed to obtain the electrolyte film; The solid electrolyte comprises the cubic phase multi-element doped lithium lanthanum zirconium oxide solid electrolyte of claim 6.

10. A solid state battery, characterized by, The solid battery comprises a positive electrode, a negative electrode and an electrolyte film between the positive electrode and the negative electrode, and the electrolyte film is the electrolyte film of any one of claims 7-8 or the electrolyte film prepared by the preparation method of claim 9.

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